Telephone magnet system



July 22, 1930. R. T. KINGSFORD TELEPHONE MAGNET SYSTEM Filed Dec 16 IN VEN TOR.

, 151 ATTORNEY.

Patented July 22, 1930 UNITED STATES PATENT OFFICE vRUSSELL T.KINGSFORD, F WYNCOTE, PENNSYLVANIA, ASSIGNOR TO ATWATEB. KENTMANUFACTURING COMPANY, 0F PHILADELPHIA, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA TELEPHONE SYSTEM Application -tiled December '18, 1926.Serial No. 155,158.

My invention relates to telephonie apparatus, and particularly to'amplifying telephones, loud speakers or radio speakers, utilized inconnection with radio receiving apparatus. y

In accordance with my invention, the electro-magnetic system comprises aplurality of spaced field yokes or frames, preferably permanentlymagnetized, having on opposite sides poles of opposite signs, withinwardly projecting pole pieces comprising overlying pole ieceextensions between 'which is received) the free end of a vibrator-yreed, armature bar, or the like, secured at its other end to theaforesaid yokes or frames or one of zthem. i

Further in accordance with my invention, the aforesaid inwardly'projecting pole pieces are bifurcated to form sets of facing pole pieceextensions; one set of which, and, preferably the set most removed fromthe point of attachment of the reed or armature bar to its supportingstructure being brought into loverlying relation, while the other set,in this case the one nearest the said point of attachment lies in asubstantially common plane to provide a shunt path for the magnetic fluxtraversing lengthwise the vibratory reed or armature.

Further in accordance with vmy invention, the air-vibrating diaphragm ortympanum of paper, metal, or other suitable material, preferably o'flarge area or diameter and preferably conical is supported solely by amember substantially non-flexible in a directioncoinciding with thegravitational plane of the diaphragm and of relatively ,greatflexibility in a plane at right angles to said gravitational plane;

Further in accordance with a preferred form of my invention, theaforesaid vibratile armature or reed extends axially of thecoil lorwinding traversed by the sound-representin current, whichcoll or windingis suitlab y supported upon stati :mary parts such as the pole pieceextensions, preferably by separate members carried thereby and soconstructed and arranged that lateral -movement of the coil or windingwith respect to the vibratile reed is prevented.

My invention resides in the system, appa-y ratus and features ofconstruction of thecharactcr hereinafter described and claimed. For anunderstanding of some of the forms my invention may take, reference isto be had to the accompanying drawing in which:

Fig. 1 is a side elevational view of a telephone magnet systemconstructed in accordance with my invention.

Fig. 2 is a vertical sectional view taken on the line 2 2 of Fig. 1looking in the direc 6, partlyin'section, showing the coil and itssupporting members.

Fig. 8 is an enlarged view, partly in ele-l vation and partly insection, of the structure shown in Fig. 7

Fig. 9 is a perspective view of a coil sup porting member. Fig. 10 showsan alternative coil arrangement which can be usedwith other parts asbefore described. W

Referringt'o the drawings, there is illus,- trated a magnet systemcomprising the platelike yokes or frames A, A, preferably duplicate incharacter and each cut away or recessed interiorly thereof to define asubstantially rectan lar opening. `Disposed between the yo es A, A isthevibratile mem ber, reed or armature 1 on either side of which, adjacentone end thereof, is disposed a washer 2 of magnetic or non-mageticInaterial, preferably, however, non-magetic in character as brass or thelike, through which washers and the perforated end of reed 1 extends abolt 3 or the like for holding the parts in assembled relation. To theend that the yokes A, A may be held in parallel relation orsubstantially so, at the end thereof removed from the bolt 3, there isprovided the spacing Washer 4, likewise either magnetic or non-magneticin character, but preferably non-magnetic and of brass or the like, andwhose thickness corresponds substantially with the combined thickness ofreed l and Washers 2. Passing through this end of frames A, A and washer4 is the bolt 5, preferably corresponding with bolt 3.

- Secured between the yokes or frames A, A by the bolts of screws 6 arethe inwardly extending pole pieces 7, each of which isv bifurcated toform the spaced pole piece extensions or end portions 8 and 9. Theextensions 8 are offset in opposite directions and disposed inlsuperposed or spaced relation for the reception of the free end ofreed 1. The pole piece extensions 9 are not offset, as are theextensions 8, but are extended in suitable close relation to the edgesof the reed 1 to thereby provide a shunt path for the magnetic fluxthreading through said reed by virtue of the coil or winding associatedtherewith and which is traversed by fluctuating voice or soundrepresenting current, such as exists, for example, in the anode circuitof a detector or audio frequency amlifier as utilized commonly in radioreceivmg circuits. g

Vthile I prefer to o'set the pair of pole extensions 8 which areadjacent the free end of the reed, the reverse arrangement of offsettingthe pair 9 and keeping the pair 8 not offset and in close' relation tothe edges of the reed may also be used.

Referring to Fig. 9, there is illustrated for the aforesaid coil C amounting or supporting member M, preferably of brass or othernon-magnetic materia-l. Member M comprises a relatively plane surface 10terminating in the flange or angular portion 11, which, in turn,terminates in the portion 12 extending substantiall parallel withsurface 10 and from which and the member 11 extends the portion 13substantially at right angles with resv ect to both. Adjacent its otherend, mem er 10 'is offset as indicated at l0 and the portion thus odsetterminates in the flange or angularportion 14 provided with the angularextensions 14.

For supporting the-coil C and holdin the same in suitable spacedrelation witr respect tothe reed 1, there are utilized 'two of thesupportingymembers M. The pocket formed at the end of each member M bythe intersecting portions 11, 12 and 13 is fitted over a pole pieceextension 8 in such manner that portion llengages that face of theextension 8 nearest the spaced extension 9 Fig. 5, while portion 12overlies the outer pole piece extension face or that face parallel withand most removed from reed 1 Fig. 7 and portion 13 overlies the end ofsaid pole piece extension. Accordingly, the plane surfaces l() of eachmember M extend toward the pole piece extensions 9 substantially in theplane of their respective outer surfaces. However, since the odsetportions 10a of each member M extend toward each other, and since theflange 14 overlies the pole piece extensions 9, Fig. 1, it results thatthe odset portions 10a constitute shoulders, each of which engages theface of a pole piece extension 9, Fig. 8.

The coil C may be supported directly on the aforesaid members M butpreferably there is interposed therebetween the layer or strip 15 ofpaper, cloth or the like.

The members M function primarily as a support for the coil C to hold thesame in suitable spaced relation with respect to the vibratory end ofthe reed 1. Moreover, due to their construction lateral or transversemovement of coil C with respect to the reed 1 is prevented sinceportions 13 of members M, respectively, engage the ends of pole pieceextensions 8 and the offset portions 10=L constitute shoulders disposedbetween the pole piece extensions 9. By utilizing the structure justdescribed, lateral movement in either direction of both ends of coil Cwith respect to reed lis revented.

T e coil C may have its terminals 16, 1G connected to binding posts 17,17a mounted in spaced relation on a member or plate 18 preferably heldin place on a yoke or frame A by the aforesaid bolt or screw 5. Member18 may be formed of suitable insulating material, as a phenolcondensation product or hard rubber, but preferably comprises a fabric,as linen or canvas impregnated in a phenol condensation product. 1

As hereinbefore described, the reed l is clamped between the yokes A, Aby the bolt or screw 3. Between this screw and the coil C and preferablyextending through ears 19 of okes A, A are the members or screws 20 an21, each of which at its end engages an opposite face of the reed 1.Accordingly', only that portion of said reed to the left of the screws20 and 21, Figs. 1, 3 and 6, partakes of pivotal movement. Aside fromthus determining by their position the length' of the pivotal action ofreed 1, the screws 20, 21 have the added function that by adjustmentthereof, the reed may be adjusted with respect to the coil C to vary thedimensions of the air ap between its free end and the adjacent aces ofpole extensions 8.

The yokes or frames A, A are preferably permanently magnetized, havingpoles of opllU posite signs at opposite sides ,thereof'adjacent orcoinciding with the regions wherein are attached the pole pieces "I?.

Extending laterally from the reed 1 is the member or bar 22, to which issecured the air-vibrating member, diaphragm or tympanum T.

Member 22 may besecured to reed 1 in any suitable manner, preferably,however, as illustrated by riveting a block 23 to the reed and thenriveting the block and member 22 to each other.

Likewise", the diaphragm T may be secured to the member 22 in anysuitable manner. An example of a satisfactory type of construction, whenthe diaphragm T is conical, is illustrated in Fig. 6, wherein the apexof the cone is provided with a circular opening faced by the headed orturned portion of a conical member 24 of suitable durable material, asaluminum or soft steel, disposed exteriorly upon the diaphragm T.Disposed interiorly thereof is the conical facing washer or member 25,preferably of hard steel or the like. As shown, the inner portion ofmember 24 is turned or headed and encompasses the adjacent edges of thediaphragm T and member Resting on the exposed face of the member 25 arethe angularly disposed portions of a supporting member or bracket 26 ofsteel or other rigid material comprising two legs which converge to forma pocket receiving the end of member 22. Passing through alignedperforations inithe pocketed portion K of bracket 26 and the end ofmember 22 is a bolt or the like 27.

The angular portions ofbracket 26, and

members 24 and 25 may be rigidly united with.

the diaphragm T by utilizing a plurality of rivets or the like 28, eachheaded on opposite sides of the diaphragm.

As described in my co-pending application, Serial No. 155,159, filedDec. 16, 1926. the diaphragm or tympanum T should be of relatively largediameter, preferably upwards of six inches, and for both axial andtransverse vibration is, unrestricted throughout and free to vibrate atits periphery at the frequency and with the amplitude of vibrationstransmitted through the cone from its axis or center, whereat only it issecured or fixed to and comprehended inthe vbra- 'tory system comprisingin additlon the vibratory reed 1.

Under such conditions, a feature of my invention resides in theinterposition of a flexible connecting-member between the vibratory reedor armature and the cone. Referring to Fig. 6, the pivotal movement ofreed 1 imparts to the end of member 22 a to-and-fro movement in a planeextending at right angles longitudinally of the yokes A, A. Should theconnection between the vibratory armature and cone be non-flexible,

auch, for example, as is constituted by the rigid pin or bar of theprior art, the cone is given a transverse bodily to-and-fro movementwith resultant distorted or imperfect sound reproduction.

A feature of my invention resides `in the interposition of a flexible,rather than a noniexible, member between the reed and cone. Such, forexample, as the member 22 which is constructed of spring steel, phos horbronze, or the like. Due to its flexibility, this member bends or fiexesin a plane extending at right angles longitudinally of the yokes A, Aand as 'a result, due to the inertia of the cone, little or notransverse bodily movement is imparted thereto.

Where, however, the cone is unrestrained throughout and free to vibrateat its periphery as described above, the aforesaid member 22 constitutesthe sole support therefor, and, hence. should be relatively non-flexiblein the direction coinciding with the gravitational plane of the cone soas to carry the weight without flexing or bending. By way of example,the member 22 is illustrated as of substantially greater breadth thanthickness and, hence, the aforesaid result may be attainedby sosuspendin the cone that the weight is carried in the lirection ofbreadth rather than width.

To thus render the member 22 non-flexible in one direction does notresult disadvantageously, because the vibration of reed 1 does notimpart a to-and-fro movement to' the end of member 22 in the directionin which the weight of the cone is carried.

As described in my aforesaid application, Serial No. 155,159 filed Dec.16, 1926, the herein described magnetic structure having the diaphragm Tsuspended therefrom may be attached to a casing F, preferably byutilizing the same screws 6 that hold the pole pieces 7 with the yokesA, A. When the frame is constructed of magnetic material, the screws 6should be of suitable non-magnetic material, as brass. In the event thatcasing F is constructed of non-magnetic material, the screws 6 may be ofmagnetic material, if desired.

The aforesaid pole extensions 9 constitute. in effect, a path shuntingthe path between pole extensions 8 for the magnetic flux induced inthereed 1; Where the extensions 9 are brought into overlying relationwith respect to the reed 1, thereby providing two sets of' pole piecescooperating therewith, it has been found that distortion is introducedinto the sound-reproducing system. This condition probably arises due tothe fact that the reed is pivotally mounted and, hence, due to thedifferent lengths of the air gaps at the sets of pole pieces spacedunequally from the pivot, the reed, in different regions thereof, iseffected by different tractive efforts. By eliminating the tractiveeffect of pole pieces 9, the reed is attracted and repelled in but oneregion, thereby rolnoting the faithfulness of sound repro uction.

It is evident that the extensions 9 could be kept in overlying relationto the reed if located at a substantially non-vibratilepart of the reedsuch as its fixed portion, but 1 prefer the simpler construction shown.

The pole piece extensions 9 may be brought into such spaced relationWith respect to the reed 1 as may be suitable or desirable. Merely byWay of example it may be stated that excellent results have beenobtained when the gap between each pole extension 9 and the reeld l isof the order of 0.004 or 0.005 of an mc lt shallbe understood that themagnetic system herein disclosed may be utilized to actuate a disphragmof any 'desired character, as for example one which has its peripheryrestrained from vibration. Further, the magnetic system herein disclosedmay be utilized With other types of loud speaking tele- -sirabletransverse vibration occurs.

phonic apparatus, as, 'for example, in lieu of the magnetic systemsdisclosed in the prior application to Kent7 Serial No. 32,875, liled May26, 1925; Greswold, Ser-iai No. 65,076, iled'Oct. 27, 1925; or to myselfand Richter, Serial No. 41,031, tiled July 2, 1925.

It shall also be understood that the conesupportin member, as one havingthe function and c aracter of the member 22 herein disclosed, may bebeneficially utilized, when the actuating reed or armature therefor ispivotally or oscillatorily mounted, with any diaphragm or tympanum whichis sufficiently unrestrained from free vibration that unde- Partienlarly, a member of the character oit the member 22 herein disclosed,either with or without the associated magnetic system, may be associatedwith the diaphragms disclosed in the aforesaid applications to Kent,Greswold, and to in 'self and Richter.

, Instea of utilizing a single coil traversed by sound-representingcurrent and surrounding the vibratile armature bar as hereinbeforedescribed, I may utilize construction of the character illustrated inFig. 10, or equivalent, wherein each pole piece extension 8 is shown ashaving disposed thereona coil C2 so connected that when one is helpingthe permanent magnet fiux, the other is opposing it. Obviously, with theconstruction disclosed in Fig. 1,0, there may be utilized a single coiiC2 on but one pole piece extension, if found desirable. Moreover,instead of disposing the coils C2 on the pole piece extensions 8, eitheror both of the pole piece extensions 9 may have a coil C2 disposedthereon. @r a coil C2 maybe disposed on a pole piece extension 9 andanother coil C2 on a pole pieceextension 8; or a single coil C2 may bedisposed on the pole piece extensions 8, 9 of a single pole piece 7.

What I claim is: 1'. A telephone magnet system comprising ermanentlymagnetized frames, pole pieces t erefor extending from opposite sides ofsaid frames, a flexible armature bar disposed between said frames, andmeans for securing said frames and armature bar in assembled relation asa unitary structure.

2. A telephone magnet system comprising spaced Eermanently magnetizedframes, pole pieces t erefor extendin from opposite sides of saidframes, a vibratile armature bar secured adjacent its one end to saidmagnet frames and having its free end disposed ad- 'acent said polepieces, and a member carried y one of said frames and enacting with saidarmature bar in a region removed from said one end thereof.

3. A telephone magnet system comprising spaced permanently magnetizedframes, pole pieces therefor extending from opposite sides of saidframes, a vibratile armature bar secured adjacent its one end to saidmagnet frames and having its free end disposed adjacent said polepieces, and members carried, respectively, by said frames 'and extending-toward each other into contact with opposite sides of said armature barin a region removed from said one end thereof.

4. A telephone magnet system comprising spaced ermanently magnetizedframes, pole pieces therefor extending from opposite sides oi saidframes, a vibratile armature bar secured adjacent its one end to saidmagnet tramesand having its tree end disposed adjacent said pole pieces,and adjusting screws carried, respectively, by said frames and extendingtoward each other into contact with opposite sides of said armature harin a region removed from said one end thereof.

5. .A 'telephone magnet system comprising Aa mavnet trame a-'vibratilearmature bar secured adjacent its one end to said frame, and hiturcatedpole pieces forming pole piece extensions extendinn toward each otherfrom opposite sides of said frame, one pair oi said extensions overlyingeach other in spaced relation and embracing a Lfree part of saidarmature bar, and another pair of said ertensions extending toward eachother throughout their length in substantialiy a common plane andterminating closely adjacent said armature bar.

6. A telephone magnet system comprising spaced permanently magnetizedframes deiining a substantially rectangular opening, a vibratilearmature ar secured adjacent its' one end between said frames and havingits :tree end extending into said opening, and biiurcated pole lecesforming pole piece extensions extending toward each other intr. saidopening trom opposite sides of seid rames,`the pair of said extensionsmost removed rom said one end of said armature overlying each other inspaced reiation and each other from opposite sides of said frame,

a winding vtraversed by sound-representing current, a vibratile armaturebar coacting with a pair of said pole piece extensions and extendingaxially through said windingy'and means comprising a plurality ofduplicate non-magneticv members supported by said pole piece extensionsand upon which said winding is disposed. y

8. A telephone magnet system comprising a magnet frame, bifurcated polepieces-forming pole piece extensions extendin toward each other fromopposite sides of said frame, a winding traversed by sound-representingcurrent, a vibratile armature bar coacting with a pair of said polepiece extensions and extending axially through said Winding, meanscomprising ya plurality of duplicate non-magnetic members supported bysaid pole piece extensionsand upon which said winding is disposed, saidmembers being constructed and arranged to prevent transverse movement ofsaid Winding with respect to said armature bar.

9. A telephone magnet system comprising spaced permanently magnetizedframes deining a substantially rectangular opening,a

vibratile armature bar secured adjacent its'A one end between saidframes and having its free end extending into said opening, bifurcatedpole pieces forming pole piece extensions extending'toward each otherinto said opening from opposite sides of said frame, one pair of saidextensions overlying each other in spaced relation and receiving saidfree end of said armature bar, and another pair oi said extensionsextending toward each other throughout their length in sub stantially acommon plane, a Winding through which said armature bar axially extends,and members maintained in spaced position by said extensions to supportand position said Winding. ,i

10. A telephone magnet system comprising` spaced permanent-ly magnetizedframes delining a substantially rectangular opening, -a vibratilearmature bar secured adjacent its one end between said frames and havingits free end extending into said opening,bifur cated pole pieceslforming pole piece extensions extending toward each other intosaidopening from opposite sides of said frame, one pair of said extensionsoverlying each other in spaced relation and receiving said free end ofsaid armature bar, and another pair of said extensions in close relationto said armature bar and in 'substantially a common plane, a Windingthrough which said armature bar axially extends, and means forsupporting and preventing transverse movement of said winding withrespect to said armature bar comprising a plurality of duplicatemembers, each of which comprises a pocket receiving a pole pieceextension of said first-named pair and a shoulder disposed between thepole piece extensions of said secondnamed pair.

11. A telephone magnet system comprising spaced permanently magnetizedframes deining a substantiall rectangular opening, a vibratile armatureliar secured adjacent its .one end between said frames and having itsfree end extending into said opening, bifurcated pole pieces formingpole piece extensions extending toward each other into said opening fromopposite sides of said frame, one pair of said extensions overlying eachother in spared relation and receiving Said free end of said armaturebar, and another pair of said extensions extending toward each otherthroughout their length in substantially a common plane and inclose'relat-ion to said armature bar, a winding through which saidarmature bar axially extends, and means for supporting and preventingtransverse movement of said Winding with respect to said armature barcomprising a plurality of duplicate members, each of which comprises apocket receiving a pole piece extension of said first-named pair, ashoulder disposed between the pole pieceextensions of said second-namedpair, and an angular portion engaging the magnet system comprising avibratile member, a diaphragm of large area and means for securing saiddiaphragm to A.said vibratile member comprising a member havingsubstantially different iexibility in one direction than in another.

13. A loud speakingl telephone having a magnet system comprising avibratile member, a conicaldiaphragm of large area, and means forsecuring said diaphragm solely adjacent its apex to said vibratilemember coinprising a member having substantially greater fiexibility inone direction than 1n another.

14. A loud speaking telephone having a magnet system comprising avibrat'ile inember, a diaphragm of large area whose periphery isentirely free of restraint, and means for securing said diaphragm tosaid vibratlle member comprising a member having substantially differentflexibility in one direction than in another.

15. A loud speaking telephonel having a magnet system comprising anelongated vibratile member, a diaphragm of large area Whose periphery isentirely free of restraint, and means for vsecuring said diaphragm tosaid vibratle member comprising a member lla-ving substantialflexibility only in a direction coinciding with the longitudinal axis ofsaid vibratilemember.

16. A loud speaking telephone having a magnet system comprising avibratile armature, a diaphragm of large area, and a member extendinglaterally from said armature constituting the sole support for saiddiaphragm and substantially non-flexible in the gravitational planethereof and of relatively great flexibility in a direction substantiallyat right angles to said plane.

17. A. loud speaking telephone having .a magnet system comprising avibratile armature, a dia hragm of large area, and a member exten inglaterally from said armature of substantially greater breadth thanthickness and constituting the sole support for said diaphragm, thebreadth of said member coinciding with the gravitational plane of saiddiaphragm.

18. A. telephone magnet system comprising a magnet frame, bifurcatedpole pieces forming pole pieceextensions extending toward eachother fromopposite sides of said frame, one pair of said extensions overlying eachother in spaced relation, and another pair of said extensions extendingtoward each other' throughout their length in substantially a commonplane, a vibratile armature bar secured to said frame and in partreceived between said iirst named extensions and closely approached bysaid second named extensions, and a Winding traversed bysound-representing current for vibrating said armature bar.

19. A. telephone magnet system comprising a magnet frame, a vibratilearmature bar rigidly secured adjacent its one end to said frame, andbifurcated pole pieces forming pole piece extensions extending towardeach other from opposite sides of said iframe, the pair of saidextensions most removed from said one end of said armature overlyingeach other in spaced relation and receiving said armature bar at oradjacent its free end, another pair of said extensions extending towardeach other throughout their length in substantially a common plane to`regions closely adjacent said armature bar, and a winding traversed bysound-representing current through which said armature bar extends.

20. A telephone magnet system comprising a magnet structure, an armaturebar vibrating in one plane only, bifurcated pole pieces extending fromboth poles of said magnet structure into close relation with freelyvibratile portions of said armature bar, a pair of pole piece extensionsof op osite polarity situated on opposite sides o? said armature bar andin its lane of vibration, the other opposing pair ci) pole pieceextensions also situated on opposite sides of said armature bar but in aplane at right angles to its plane of vibration, and a Winding traversedby sound-representing current 'surrounding any or all of said pole pieceextensions or that portion of the armature bar which lies between thetwo pairs of pole piece extensions.

, 21. A telephone magnet system comprising a magnet structure, anarmature bar vibrating in one plane only, pole pieces extending fromboth poles of said magnet structure and each divided into two ole pieceextensions, one pair of said pole piece extensions of opposite polaritysituate on oppositeI sides of said armature bar and in parallel closerelation to freely vib'ratile faces thereof, the second pair of polepiece extensions of opposite polarity situate in close relation tononvibratifle surfaces of said armature bar, and a Winding traversedbysound-representing current surrounding any or all of said pole pieceextensions or that portion of said armature bar which lies between theone pair and the second pair of said pole piece extensions.

22. A loud speaking telephone having a magnet system comprising avibratile member, a conical'diaphragm of large area, a member passingfreely through said conical diaphragm substantially' at the apexthereof, out of contact therewith, and secured to said vibratile memberon the`convex side of said conical diaphragm, and means to attach saidconical diaphragm to said member on the concave side thereof.

23. A loud speaking telephone comprising a large diaphragm capable ofaxial and transverse vibration, a magnet system, structure co-operatingtherewith and movable in accordance with current variations of audiofrequency, and a member connecting said diaphragm to said structurehaving substantially gr'eaterlexibility in one direction than in anotherto eeet substantially solely axial vibration of said diaphragm.

24. A loud speaking telephone comprising a large diaphagm capable ofaxial and transverse vibration, an actuating member therefor havingcomponents of motion axially and transversely of said diaphragm, and amember connecting said diaphragm to said actuating member havingsubstantially greater lexibility in one direction than in another totransmit to said diaphragm substantially solely said axial component ofmovement of said actuating member.

25. A loud speaking telephone comprising a large diaphragm capable ofaxial and transverse vibration, a magnet system including an armaturehaving components of motion axially and transversely of said diaphragm,

`and a fie'xible member of Width substantially exceeding its thicknessconnecting said diaphragm to said armature to efl'ect substantiallysolely axial vibratile of said diaphragm.

26. A loud speaking telephone having a magnet system comprisingstructure comperliti ating therewith and movable in accordance withcurrent .variations -o audio-frequency, a conical diaphragm of llargearea and capable of axial and transverse Vibration, a member passingthrough said cone substantially at the apex thereof secured to saidstructure and having substantially greater flexibility in one directionthan in another to transmit substantially solely said axial component ofmovement of said structure, and means connecting said member to theconcave side of said diaphragm.

RUSSELL T. KINGSFORD.

